Effect of the edge states on the conductance and thermopower in zigzag phosphorene nanoribbons

Abstract

We numerically study the effect of the edge states on the conductance and thermopower in zigzag phosphorene nanoribbons (ZPNRs) based on the tight-binding model and the scattering-matrix method. It is interesting to find that the band dispersion, conductance, and thermopower can be modulated by applying a bias voltage and boundary potentials to the two layers of the ZPNRs. Under the certain bias voltage, the two-fold degenerate quasi-flat edge bands split perfectly. The conductance can be switched off, and the thermopower around zero energy increases. In addition, when only the boundary potential of the top layer or bottom layer is adjusted, only one edge band bends and merges into the bulk band. The first conductance plateau is strongly decreased to e 2 /h around zero energy. Particularly, when the two boundary potentials are adjusted, all the edge bands bend and fully merge into the bulk band, and the bulk energy gap is maximized. More interestingly, a pronounced conductance plateau with G = 0 is found around zero energy, which is attributable to the opening of the bulk energy gap between the valence and conduction bands. Meanwhile, the thermopower can be enhanced more than twice, compared to that of the perfect ZPNRs. The large magnitude of thermopower is ascribed to the appearance of the bulk energy gap around zero energy. Our results show that the modulated ZPNRs are more reliable in thermoelectric application.

Magnetothermoelectric transport properties in phosphorene

“…Clearly, the central n = 0 LL around E F =0 is markedly absent. Moreover, all the LLs in the positive and negative regions are somewhat asymmetric in position, which can be attributed to the absence of particlehole symmetry of the present band structure 20 . The Hall conductivity is strictly quantized due to the quantized LLs.…”

“…These are consistent with the presence of ν = 0 Hall plateau due to the lack of the valley degeneracy in phosphorene. Moreover, the positions of all the peaks in α xy are asymmetric in energy due to the spectral asymmetry 20 . In Figs.…”

“…9(a)-(c), the calculated S xx , S xy and S yx are plotted for different disorder strengths with magnetic flux φ = 2π/48. It is well known that when the magnetic field is absent, the thermopower is strongly affected by the disorder, and the peaks are suppressed even for small disorder 20 . However, in the presence of the strong magnetic field, both thermopower and Nernst signal are robust to the disorder, due to the fact that the highly- degenerated LLs dominate transport processes.…”

Crystallographic Characterization of Black Phosphorene and its Application in Nanostructures

“…The zigzag PNRs (ZPNRs) with significant edge states and armchair PNRs (APNRs) with direct band-gap have been extensively studied [13,16,17,29]. And some properties of PNRs have been verified [18,[30][31][32][33][34][35][36], such as the effect of edge states on conductance and thermalpower [37], the influence of vacancy defects on electron structure and transport [38,39], and the electric tunable edge-pseudospin valve [40].…”

Width Dependent Two-Photon Absorption in Monolayer Black Phosphorus Nanoribbons

“…1) are enough to describe the electronic band structure of phosphorene [21] with hopping energies t 1 =−1.22 eV, t 2 =3.665 eV, t 3 =−0.205 eV, t 4 =−0.105 eV, and t 5 =−0.055 eV. A uniform vertical electric field E v will result in a staggered potential elE v between the upper (µ i =1) and lower (µ i = −1) sublayers due to the puckered structure [36,38]. Applying a transverse electric field E t will shift the on-site energy to eE t y i with y i the atom coordination in the y-direction, and U i is the impurity potential.…”